Abstract: Aiming at the problem of sensitive load operation interruption caused by voltage sag of power distribution lines, and based on the analysis and comparison of the advantages and disadvantages of existing voltage sag control measures such as solid-state switch, uninterruptible power supply, and dynamic voltage regulator, a voltage sag control scheme based on fast switching and dual-power-supply fast switching is proposed,and its key technologies and working principle are described in detail, which offers a new idea for voltage sag control.